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排序方式: 共有642条查询结果,搜索用时 15 毫秒
631.
Krijn Baptist Trimbos Joyce Broekman Rosemarie Kentie Cees J. M. Musters Geert R. de Snoo 《Journal of Ornithology》2009,150(4):915-920
In the context of population genetic research, a faster and less invasive method of DNA sampling would allow large-scale assessments
of genetic diversity and genetic differentiation with the help of volunteer observers. The aim of this study was to investigate
the usefulness of eggshell membranes as a DNA source for population genetic research, by addressing eggshell membrane DNA
quality, degeneration and cross-contamination. To this end, a comparison was made with blood-derived DNA samples. We have
demonstrated 100% successful DNA extraction from post-hatched Black-tailed Godwit (Limosa limosa) eggshell membranes as well as from blood samples. Using 11 microsatellite loci, DNA amplification success was 99.1% for
eggshell membranes and 97.7% for blood samples. Genetic information within eggshell membrane DNA in comparison to blood DNA
was not affected (F
ST = −0.01735, P = 0.999) by degeneration or possible cross-contamination. Furthermore, neither degeneration nor cross-contamination was apparent
in total genotypic comparison of eggshell membrane DNA and blood sample DNA. Our research clearly illustrates that eggshell
membranes can be used for population genetic research. 相似文献
632.
Meritxell Costa Albert Rosell Elena Álvarez-Marimon Antonio Zorzano Dimitrios Fotiadis Manuel Palacín 《Protein expression and purification》2013,87(1):35-40
Human heteromeric amino acid transporters (HATs) play key roles in renal and intestinal re-absorption, cell redox balance and tumor growth. These transporters are composed of a heavy and a light subunit, which are connected by a disulphide bridge. Heavy subunits are the two type II membrane N-glycoproteins rBAT and 4F2hc, while L-type amino acid transporters (LATs) are the light and catalytic subunits of HATs. We tested the expression of human 4F2hc and rBAT as well as seven light subunits in the methylotrophic yeast Pichia pastoris. 4F2hc and the light subunit LAT2 showed the highest expression levels and yields after detergent solubilization. Co-transformation of both subunits in Pichia cells resulted in overexpression of the disulphide bridge-linked 4F2hc/LAT2 heterodimer. Two sequential affinity chromatography steps were applied to purify detergent-solubilized heterodimers yielding ~1 mg of HAT from 2 l of cell culture. Our results indicate that P. pastoris is a convenient system for the expression and purification of human 4F2hc/LAT2 for structural studies. 相似文献
633.
Demographic rates such as recruitment and survival probability can vary considerably among populations of the same species due to variation in underlying environmental processes. If environmental processes are spatially correlated, nearby populations are expected to have more similar demographic rates than those further apart. Breeding populations and foraging ranges are spatially segregated in colonial seabirds, making them ideal for studying spatial patterns in demographic rates and their effects on local population dynamics. Here we explored variation in age-dependent survival probabilities across 14 colonies of Herring Gulls Larus argentatus breeding along the Dutch North Sea coast. We used long-term mark–recapture data of marked fledglings to estimate survival, and estimated spatial autocorrelation of survival probabilities. We assessed whether survival until recruitment age or until 10 years old (close to their expected lifespan) explained variation in population trajectories of each colony. Juvenile and adult survival showed a strong, but different, north-to-south gradient in survival probability, with lower juvenile but higher adult survival in northern colonies than southern colonies, whereas the spatial pattern of immature survival was less distinct. Neither recruitment nor the proportion of 10-year-old adults alive predicted whether a colony collapsed, declined, remained stable or increased. The distinct spatial pattern in survival suggests variation in regional food availability, which do not seem to drive local population dynamics. The absence of a link between survival and colony trajectories implies that connectivity between populations plays an important role affecting population dynamics. 相似文献
634.
635.
Louis J. Ignarro Rosemarie A. Gross 《Biochimica et Biophysica Acta (BBA)/General Subjects》1978,541(2):170-180
Guanosine 5′-tetraphosphate (GTP4) stimulated mammalian adenylate cyclase activity at concentrations down to 1 μM. Greater stimulatory activity was apparent with lung than with heart, brain or liver from the rat. At a concentration of 0.1 mM, GTP4 stimulated lung adenylate cyclase activity from rat, guinea pig and mouse about four-fold. Other guanine nucleotides such as GTP, GDP, GMP, guanosine 3′, 5′-monophosphate and 5′-guanylylimidodiphosphate (GMP · PNP) also stimulated mammalian adenylate cyclase activity. GMP · PNP irreversibly activated, whereas GTP4 and GTP reversibly activated adenylate cyclase. Adenosine 5′-tetraphosphate (ATP4) stimulated rat lung and liver but inhibited rat heart and brain adenylate cyclase activities. Lung from guinea pig and mouse were not affected by ATP4. The formation of cyclic AMP by GTP4-stimulated rat lung adenylate cyclase was verified by Dowex-50 (H+), Dowex 1-formate and polyethyleneimine cellulose column chromatography. GTP4 was at least three times more potent than 1-isoproterenol in stimulating rat lung adenylate cyclase activity. The β-adrenergic receptor antagonist propranolol blocked the effect of 1-isoproterenol but not that of GTP4, thus, suggesting that GTP4 and β-adrenergic agonists interact with different receptor sites on membrane-bound adenylate cyclase. Stimulation of rat lung and liver adenylate cyclase activities with 1-isoproterenol was potentiated by either GTP4 or GMP. PNP, thus indicating that GTP4 resembles other guanine nucleotides in their capacity to increase the sensitivity of adenylate cyclase to β-adrenergic agonists. Stimulation of adenylate cyclase activity by guanine derivatives requires one or more free phosphate moieties on the 5 position of ribose, as no effect was elicited with guanine, guanosine, guanosine 2′-monophosphate, guanosine 3′-monophosphate or guanosine 2′,5′-monophosphate. Ribose, ribose 5-phosphate, phosphate and pyrophosphate were inactive. Pyrimidine nucleoside mono-, di-, tri- and tetraphosphates elicited negligible effects on mammalian adenylate cyclase activity. 相似文献
636.
PGE2 and PGF2 alpha in the nasal lavage fluid from healthy subjects: methodological aspects 总被引:1,自引:0,他引:1
I Ramis J Serra J Roselló C Picado E Gelpi A A Vidal 《Prostaglandins, leukotrienes, and essential fatty acids》1988,34(2):109-112
Prostaglandins E2 and F2 alpha were estimated in nasal secretions from ten healthy volunteers by high performance liquid chromatography and radioimmunological assay. Prostaglandin concentrations determined in five consecutive nasal washes with saline at room temperature showed that the nasal mucosa was stimulated after instillation. A substantial increase of basal levels was associated with the second nasal lavage. In all volunteers aspirin treatment inhibited prostaglandin release. 相似文献
637.
638.
639.
To determine the possible activity of cyclooxygenase and lipoxygenase like enzymes in Drosophila melanogaster, we have investigated whether fly homogenates can biosynthesize prostaglandins and HETEs. Incubation of fly extracts with AA yields a mixture of 15- 12- 9- and 8-HETE as detected by selected ion monitoring GC-MS. Also the combination of HPLC-RIA using a PGE antibody shows the presence of endogenous PGE2 immunoreactivity in the extracts (405 pg/g in males and 165 pg/g in females). We have also detected the presence of lipoxygenase like immunoreactivity in the reproductive male system by using immunocytochemical techniques in whole body sections of the fly as well as reactivity in the digestive system of both males and females. Finally, we have not been able to detect endogenous AA in the fly by GC-MS methods. However, estimates by GC-MS of the total body fatty acids indicate substantial amounts of potential AA precursors. 相似文献
640.